Hydraulically actuated drop hammer



N v195s w. BRAUER 2,861,486

HYDRAULICALLY ACTUATED DROP HAMMER Filed May 14, 1956 3 Sheets-Sheet lINVENTGP Nov. 25, 19 58 W. BRAUER HYDRAULICALLY ACTUATED DROP HAMMER 3Sheets-Sheet 2 Filed May 14, 1956 I INVENI'OQ Nov. 25, 1958 w, BRAU'ER2,861,486

HYDRAULICALLY ACTUATED DROP HAW/{ER Filed May 14, 1956 5 Sheets-Sheet 5INI/ENI'OP H.31 ciuep United States Patent HYDRAULICALLZ acrparnn DROPHAMMER Willi Brauer, Cohnrg, Germany, assignor to Langenstein & SchemannA. G., Ernsthutte-Coburg, Germany Application May 14, 1956, Serial No.584,771

Claims priority, application Germany May 13, 1955 9 Claims. (Cl. 78-42)The present invention relates to an improvement in the art directed todrop hammers.

More particularly, this invention relates 'to a hydraulically actuateddrop hammer in which a vertically movable tup cooperates with an anvilduring a hammering operation.

Specifically, the invention is concerned with a hydraulically actuateddrop hammer in which the tup is carried by the rod of a piston that isdisposed in a vertically extending cylinder and which cylinder isprovided at its lower end with an opening communicating with a fluidline or conduit through which liquid enters to raise the piston in itscylinder and through which liquid exhausts from the cylinder during ahammering operation. The hammer includes means for controlling the flowof liquid so as to alternately permit it to flow under pressure into thecylinder below the piston and to escape or exhaust from the cylinder.Further, the cylinder includes an upper wall or top construction thatcloses the space above the piston so that air or any other gaseousmedium above the piston is compressed when the piston rises and expandsas the piston descends.

In drop hammers of this type the fall of the tup is braked by the factthat during descent of the tup, the descending piston has to displacethe liquid which raised the piston to its upper position.

Accordingly, the present invention has for an object to accelerate thedescent of the tup and increase the energy of the blow, that is, thehammering impact of the tup and also to increase the number of blowsstruck per minute.

It is a further specific object of the invention to provide meansoperable to vary the speed of descent of the tup over wide limits andthus to also vary the energy of the blow or impact and the number ofblows struck per minute.

It is a particular object of the invention to provide means operable toincrease the quantity of air trapped above the piston at will, that is,as desired and a further feature of the invention consists in theparticular construction of the means operable to increase the quantityof trapped air.

It is a more specific object of the invention to provide in combinationwith a hydraulically actuated drop hammer of the type in which avertically movable tup cooperates with an anvil and in which avertically disposed cylinder slidably receives a piston the rod of whichcarries the tup, a liquid flow initiating and control means operable toalternately introduce liquid under pressure into the lower portion ofthe cylinder to raise the piston and thus the tup and to permit exhaustof liquid from the cylinder so that the piston and thus the tup falls,and in falling displaces the liquid from beneath this piston, and achamber means operably associated with the top of the cylinder and invalve controlled communication therewith, said chamber meansaccommodating a supply of 2,861,486 Patented Nov. 25, 1958 gaseousmedium under pressure whereby said medium can be selectively andcontrollably introduced into the upper portion of the cylinder toincrease the quantity of gaseous medium acting on the top of the pistonduring its descent to augment the fall of gravity and thus increase theenergy of the blow struck by the tup.

It is a still more specific object of the invention to provide ahydraulically actuated drop hammer including a vertically disposedcylinder, a piston movable in the cylinder, a tup carried by the piston,means operable to establish a flow of liquid under pressure into thelower portion of the cylinder to raise the piston and thus the tupincluding control means operable to rapidly exhaust liquid from thecylinder beneath the piston whereby the tup descends during a hammeringoperation, a partition means crossing the cylinder and defining achamber above the upper position of the piston, valve controlled conduitmeans through the partition providing communication between the chamberand the part of the cylinder accommodating the piston and conduit meansin communication between the chamber and the cylinder subjacent thepartition operative to permit plural reciprocations of the piston tocompress and supply the chamber with a quantity of compressed gaseousmedium for subsequent controllable introduction through the partitionmeans and into the cylinder above the piston to variably augment thegravitational descent thereof during hammering.

Further and more specific objects will be apparent from the followingdescription taken in connection with the accompanying drawingsillustrating two embodiments of the invention, and in which:

Figure 1 shows a drop hammer partly in elevation and partly in section;

Figure 1a is an enlarged vertical sectional view of the upper part ofFigure 1; and,

Figure 2 shows a detail of Figure 1 on a larger scale.

A base 1 of the drop hammer supports an anvil 2 on to which a tup 3,guided for upward and downward movement in guiding rails 4, can drop.The guiding rails are mounted on two uprights 5 which together support aworking cylinder 6 and an oil container or reservoir 7. The cylinder 6is vertically disposed, secured to the uprights 5 by means not showninthe drawings, and accommodates a working piston 8 which is rigidlyconnected to the tup 3 through the intermediary of a piston rod 9. Thearrangements are such that when the tup 3 is in .its lowest position thelower face of piston 8 is slightly above an opening 10 through whichliquid under pressure can be supplied to cylinder 6 beneath the piston 8to raise the piston and from which the liquid is forced out of thecylinder when the piston descends during hammering. A hydrostatic pump11, for instance a gear pump, is used for establishing a flow of liquidunder pressure. The pump 11 is coupled, through the intermediary of aclutch 12, with an electric motor 13 which receives current fromelectric leads 14, When a switch, not shown in the drawing is closed.-'The liquid for instance, oil, which fills the container 7 up to thelevel denoted at 16, is sucked out of the container through a suction orintake pipe 15 by the pump 11. The pump drives the oil through apressure duct 17, passing behind the cylinder 6, into a chamber 17abranched from duct 17 and closed by a non-return or check-type inletvalve 18 which permits liquid under pressure to flow out of chamber 17::into pipe or duct portions 44, 45 described hereinafter and thus throughopening 10 into the cylinder but prevents reverse flow of liquid fromthe cylinder back into. chamber 17a and pressure duct 17. The pressureduct 17 extends beyond chamber 17a and terminates in a branched bypassportion 19 adapted to be controlled by a piston-type valve body 20. Thevalve body 20 is vertically movable in a cylinder portion 21 asdescribed hereinafter. Therefore, when the by-pass portion 19 is open,the pump sucks oil through the intake pipe and forces it to flow throughthe by-pass portion 19 and back into the container or reservoir 7. Whenthe valve body 20 is lowered, its lower 'end- 20 closes the bypass ductportion 19. The oil which the pump 11' continues to deliver then liftsthe inlet valve 18 and flows upwards, out of the chamber 17a, into thepipe or duct portions 45 and 44 and thence through opening 10 into thecylinder 6. For upward and downward movement in the cylinder 21 thevalve body 26 is articulated by means of a link 22 connected to a lever23 rigid with a horizontally disposed rockshaft 24 which is turnablymounted in bearing supports 25 and 26. Therefore, as the rockshaft 24 isturned up or down, that is, clockwise or counterclockwise by meansdescribed hereinafter, the valve body 20 is moved upwards or downwards.

Two other valve control levers 27 and '28 are also rigidly secured tothe rock'shaft 24. They serve to actuate stroke-length controlling valve29 and cylinder exhaust or outlet valve 30, respectively, which aredescribed in detail hereinafter with reference to Figure 2. A rockshaftturning lever 31 is rigid with the rockshaft 24, and acontrol rod 32provided with a bifurcated end portion or fork 33 is pivoted to theendof lever 31. A pin 34 passes through the bifurcated end or fork 33and through the lever 31, and is mounted rigidly either in the lever 31-or in the fork 33, while the other of these two parts is rotatable aboutthe pin 34. A stop or abutment 35 is adjustably clamped on the controlrod 32 so that it can be fixed in different positions axially of controlrod 32. A bell-crank lever 36 including arms 36a and 36b is rockableabout a pivot 37 that is secured to one of the uprights 5. The weight oflever arm 36a tends to rotate 1 the bell-crank lever arms 36a, 36b, in acounterclockwise direction. Lever arm 36a is provided on its free endwith a blocking member or fork 33 by means of which the lever arm 36acan impinge against the stop adjustable abutment 35. A fixed stop orabutment 39 is rigid with the upright 5 so that lever arm 36a, after aslight downward movement impinges against this fixed stop 39 to limitdescent of the control rod 32 and thus counterclockwise turning ofrockshaft 24. The lever arm 36]) has a rounded end 40 which in theposition shown in the drawing bears laterally against the tup 3. The tup3 has an inclined cam surface 41 so arranged as to abut against therounded end 49 of lever arm 36b when the tup moves upwards, so that thebell-crank lever arms 36a, 36b, the position of which was previouslydetermined by the stop or fixed abutment 39, effect a slight rockingmovement about the pivot 37, during which movement the fork 38 lifts thestop or abutment 35, and thus the control .rod 32 into the positionshown in the drawing, if .these parts have not already been previouslymoved into the position shown in the drawing. In the position shown inthe drawing, the rounded end 46 of lever arm 36!) bears against the sideof the tup, so that descent of the control rod 32 and its abutment 35 isblocked or prevented by the position of the bell-crank lever arms 36a,36b.

The opening 10 in the lower part of the cylinder 6 is connected to aninlet pipe portion 44 branched off of pipe portion 45 which is incommunication with the chamber 17a downstream of the non-return oil orliquid inlet valve 13. A damping cylinder 46 is also conected to thepipe portion 44 through the intermediary of a branch pipe 47 and adamping piston 48 slides in the damping cylinder and makes aliquid-tight seal therein. The damping piston 48 is urged downwardly bya compression spring 49 which bears against the top of the dampingcylinder 46. Damping piston 48 is moved upwards only when the oilpressure in the branch pipe 47 is so great as to be able to overcome theinitial stress in the spring d9.

The pressure duct 17 carries, between the outlet of pump 11 and chamber1711, a depending pipe 5'0 that accommodates a non-return,suction-operated liquid make-up valve 51 adapted to prevent oil orliquid fiowing out of pressure duct 17, but which under certaincircumstances permits oil to pass out of the container 7 into the duct17. In the top of the container 7 is an opening 52, which produces theeffect that the top surface of the oil in container '7 is always actedon by atmospheric pressure. In an alternative form of construction,however, the opening 52 could be closed so that the air above thesurface of the oil level can be placed under air pressure varying, forinstance, between two and four atmospheres as the height of the oillevel changes.

The bottom end of the control rod 32 carries a fork 32a which is pivotedto a lever 53 rigid with another rockshaft 54 that is turnably mountedin bearings 53 mounted on the base 1 of the drop hammer. A pedal lever56 is also non-rotatably secured to the rockshaft 54, so that when theoperator presses the lever 56 with his foot the control rod 32 is raisedand the valve controlling rockshaft 24 is turned.

The outlet valve controlling lever 23, rigid with rockshaft 24, has itslower end bifurcated to form a fork 57 engageable beneath a cross-bar 53rigid with the stem of a piston-type valve body 59. The outlet orexhaust valve generally denoted at 30 includes a casing portion at theterminal end of pipe portion 45 within which is a vertically disposedoutlet pipe 69. The space around the outlet pipe is an annular chamberand a plurality of bores or openings 61 provide communication betweenthe annular chamber and the outlet pipe 60. The valve body 59 controlsfluid communication between pipe por tion 45 and the outlet pipe 60. Inthe position shown in Figures 1 and 2, the fork 57 is not yet in contactwith the cross-bar 58, and it will come into contact therewith onlyafter the control rocketshaft 24 has been turned or rotated slightly inthe clockwise direction. When the rockshaft 24 rotates further, the fork57 will lift the crossbar 58 and therefore the valve body 59. As stated,pistontype valve body 59 slides in outlet pipe 6b and has a flange 60abearing on the top end of this pipe, so that the pistontype' valve body59 cannot descend lower than the position shown in full lines in Figure2. However, when the piston-type valve body 59 is raised so that itslower end surface is in the position 5% shown in dot-dash lines inFigure 2 the openings 61 are exposed. In this case, therefore, the oilin cylinder 6 and the pipe portions 44, 45 can flow out through theopenings 61 into the outlet pipe 69 and downward into the container 7,so that the tup descends abruptly.

Pipe portion 45 carries the casing 29' of stroke length controllingvalve 29. A small pipe 63a provides communication between pipe portion45 and valve casing 29. The casing is provided with an outlet bore oropening 63 of small diameter to which a bleed pipe 64 is connected. Thecasing 29' is cylindrical, and a piston-type valve body 62 having atransverse bore 62a therethrough is slidably mounted therein formovement between a lower position, preventing passage of oil throughvalve casing 29 and an upper position placing bore 62a in register withpipe 63a, and the outlet bore or opening 63. The bottom end 64a of thebleed pipe 64 is open and in free communication with the oil in the oilcontainer 7. In the position shown in full lines in Figure2, the valvebody 62 closes the bore 63. However, when the valve body 62 is raisedslightly, it exposes the outlet bore 63, so that oil under pressure inthe pipe portion 45 can flow out of the bore 63 through bleed pipe 64and into the oil container, thus allowing the tup to slowly descend. Thespace above the valve body 62 communicates through a pipe 65 with theair space above the surface of the oil. A bore 29a in the lower end ofvalve casing 29, by a pipe not shown, places the space beneath valvebody 62 in communication with atmosphere. The valve body 62 is mountedon a piston rod 66, the upper end of which is connected by pin 67 to twoarticulated links 68, which are themselves rotatable on a pin 69 mountedon the end of valve control lever 27.

The cylinder 6 is elongated, and a transverse partition wall 71 dividingthe cylinder into two portions, the lower portion accommodating piston 8and the upper portion constituting an air-receiving chamber 75. In thepartition wall 71 is mounted a manually operable air flow controllingvalve 73, adjustable by means of a hand lever 72 between an openposition shown in full lines, and a closed position shown in dot-dashlines, Figure 1a. The air chamber 75 above the partition wall 71 is alsoclosed, and mounts a pressure gauge 74. In addition, the air chamber 75has an outlet opening closed by a valve body 76, acted on by acompression spring 77 urging the valve body 76 into the closed position.On the valve body 76 there is a valve stem provided with a handle 78 sothat the valve body can be manually lifted, not only by excess airpressure in the chamber 75 but also, when desired, by hand, against theaction of the spring 77. The wall of the cylinder 6 has an opening 6communicating with the space 70 above the piston, and to which there isconnected a pipe 79 opening into a casing 80. The casing 80 is disposedadjacent cylinder 6 and includes an air inlet chamber 80 and an airoutlet conduit 88 through which air enters into air chamber 75. Betweenthe air inlet chamber 80 and the air outlet 88 is a non-return air flowcontrolling valve 81 governing communication between the air inletchamber 80', and the pressure chamber 75 when the pressure in thechamber 80' is greater than in the chamber 75. For this purpose, thestem of valve 81 carries a head 82 disposed outside the valve casing 80against which head a stop 83 can be engaged. This stop 83 is rotatablyor rockably secured to the top end of the cylinder 6 and can be broughtinto one position in which it blocks upward movement of head 82 and thusprevents the valve 81 from opening, and another position in which itallows the non-return air flow controlling valve 81 to open. In thecasing 80 there is a second non-return air check valve 84 which allowsair to enter the chamber 80' from outside, but does not allow any air toescape from this chamber.

In the top right-hand portion of the drawing an apparatus is shown indot-dash lines which can take the place of the casing 80 and valvestherein, if a simple manner of operation of the hammer will suffice tomeet the requirements. In this form of the invention the pipe 79 isextended by a pipe portion 79a to which is connected an air flowcontrolling valve 85 that can be opened and closed as-desired and whichis in communication with a compressed air container 86 through a duct87.

The manner of operation of the drop hammer will now be first of allexplained without reference to the parts provided above the transversepartition wall 71. The valves 73 and 76 may be open.

When it is desired to operate the hammer, the motor 13 is started sothat the pump 11 sucks oil through the intake pipe 15 and drives saidoil through the pressure duct 17, chamber 17a, the non-return inletvalve 18, the inlet pipe portion 44 and the opening 10 to the undersideof the piston 8. Consequently, the piston 8 rises into the positionshown in the drawing, taking with it the tup 3, the cam surface 41 ofwhich, shortly before reaching the position shown in the drawing, rocksthe bell-crank lever arms 36b, 36a slightly so that the fork 38 engagesbeneath the adjustable abutment or stop 35, and thereby lifts thecontrol rod 32. This turns the rockshaft 24 far enough to cause thevalve body vto open the by-pass duct 19. Therefore, the oil nowdelivered by the pump 11 flows back into the container through theby-pass duct 19. Reverse flow of pressure oil from the cylinder 6 is notpossible, since the nonreturn inlet valve 18 is closed, and neither ofvalve "6 and 29 are open. On the contrary, the valve bodies of these twovalves are in the positions shown in full lines in Figure 2. If it isdeslred to drop the tup 3 from a height less than that shown in thedrawing, a slight pressure is exerted on the pedal lever 56, so that therockshaft 54 turns and lifts the control rod 32. The latter then turnsvalve controlling rockshaft 24 far enough to move the piston-type valvebody 62 upwards to expose the opening 63 in casing 29. The exhaust oroutlet valve 30 is not yet opened, since the ends of the fork 57 havenot yet engaged and lifted the crossbar 58. The tup 3, therefore,descends slowly as pressure fluid slowly escapes through the narrow boreor opening 63. If the operator now wishes to deliver a blow, hedepresses the lever 56 abruptly and hard with his foot. This causes thecontrol rod 32 to'rise, and rapidly turn valve controlling rockshaft 24so far that the outlet openings 61 in outlet pipe 60 are exposed by theresulting upward movement of piston-type valve body 59. The liquidunderneath the working piston 8 now flows through the largecross-sections of the openings and pipe portions 10, 44, 45, 61 and 60so rapidly that the tup 3 and piston 8 come down hard, almost at thespeed of free fall. This dropping movement moreover, is not interruptedif the operators foot releases the lever 56, since the outflowing liquidin the pipe portion 45 and 60 has still so much pressure that itcontinues to keep the lower end surface 59a of the pistontype valve body59 in the dot-dash line position 59b. After the rapid depression of thelever 56 the control rod 32 descends owing to its own weight and therebyturns the rockshaft 24, so that the lever 23 turns clockwise, causinglink 22 to move valve body 20 down to close the by-pass duct 19. Thevalve body 59 is abruptly dragged down at, but not before the momentwhen the tup 3 strikes the anvil 2. At this moment the vigorous flow ofoil from the cylinder 6 ceases, so that the liquid still in the outletpipe 60 must abruptly decrease its velocity, since it has behind it noflowing oil, or only the oil delivered by the pump 11. The sharpdecrease in the velocity of the liquid in the outlet pipe 60 exerts asucking action on the end surface 59a of the piston-type valve body 59,so that this valve body is dragged downwards and closes the outletopenings 61. As soon as the openings 61 are closed, the liquid which thepump 11 continues to deliver has no outlet other than through opening 10into the cylinder 6, so that the piston and the tup 3 are raised againas soon as the blow has been completed. When tup 3 impacts a workpiece,it often rebounds upward, thus moving piston 8 upwards. During therebound of the tup a vacuum may existfor a short time beneath theundersurface of piston 8 and if the supply of liquid from pump 11 is notsufficient to fill the thus enlarged space beneath piston 8, thenon-return liquid make-up valve 51 opens due to the upward reboundingmovement of piston 8, liquid is sucked out of the container 7 throughpipe 50 and past this valve 51.

The damping cylinder performs the function of damping sudden violentsurges that may occur for instance when the valve body 20 closesabruptly. The damping piston 48 then moves upwards for a short timeunder the action of any excessively high pressure, so that an injuriousexcessive increase in the oil pressure is avoided. The parts of the drophammer described above are by themselves sufficient to permit verysimple control of the hammer merely by means of the lever 56, and inparticular, to enable the force of the blow delivered by the tup 3 to beregulated in an extremely simple manner. The apparatus describedhereunder makes possible a further change in the force of the blowdelivered by the tup.

Let it be assumed that the non-return air flow controlling valve 81 isheld closed or locked. If the manually operable air flow controllingvalve 73 is closed,

the air space 70 above the piston 8 is: under approxi-- matelyatmospheric pressure. If the piston 8 is driven upwards hydraulically inthe manner described above, the air in the space 70 above the piston iscompressed. On the one hand this causes the upward movement of thepiston to be braked towards the end of its stroke, and on the other handthe compressed air represents a reservoir of energy which during thedownward movement of the piston restores the work absorbed during theupward movement of the piston, and thereby additionally accelerates thedescending piston. Such arrangements are known in drop hammers. Thepresent invention aims at making the manner of operation of the energyreservoir variable, in order in this way to obtain a more or less rapidsuccession of blows as required. This can be achieved if the parts.shown in dot-dash lines are present in an apparatus that does not havethe parts shown in full lines above the partition wall 71.

It, When the piston 8 is down, compressed air is admitted to the space70 from the container 86 by actuation of the valve 85, then after thevalve 85 has been closed again the subsequent hammer blows will besubstantially harder than before, since the descending piston 8 and tup3 will then descend at a much greater speed than that of free fall,since a strong air pressure will be additionally exerted on the top ofpiston 8 until it reaches its lowest position i. e. until the blow isdelivered. The strength of the blow can be reduced again by letting someof the air out of the space 70.

Since the manner of operation described above necessarily required acharged compressed air container 86, the construction of the hammershown in full lines is preferred. For this purpose, the adjustable stop83 which can be termed a valve blocking or locking means which keeps thenon-return air flow controlling valve 81 closed is moved to a positionpermitting upward movement of valve 81. In addition, the valve 73 isclosed. If the piston 8 is now made to slide upwards and downwardsseveral times, the component parts above the partition wall 71 causesthe piston to operate as a pump. During the downward movement of thepiston '8, air is sucked in from the outside through the nonreturn valve84. This quantity of air is driven through the non-return air flowcontrolling valve 81 into the the pressure chamber 75 when the pistonmoves upwards. The manometer or pressure gauge 74 indicates the pressurein the pressure chamber 75. Any excessive pressure which might becomedangerous to the drop hammer escapes through the safety valve 76. If itis now desired to operate the hammer, this can be done either with themanually operable valve 73 open or with said valve closed. The wholeavailable compression space comprised by the total volume of the space70 and chamber 75 can thus be divided as desired. There are then twopossible ways of operating the hammer. If it is operated using thepressure space 7%, strong compression of air takes place in the space 70at the end of the upward potential movement. The energy of this air,however, is not so great as the potential energy of the combined volumeof space 70 and chamber 75. If the hammer is operated using both space70 and chamber 75 in communication with one another, a very strongpressure is exerted on the top of piston 8 even at the end of thedownward movement of the tup 3. In this connection, the quantity of airor gas above the piston in the cylinder is so greatly increased as tohave a pressure greater than atmospheric pressure, for instance, 3.5 ormore atmospheres, when the piston is down,

" I'claim:

l. A hydraulically actuated drop hammer, including a vertically disposedcylinder, a piston movable in the cylinder, a tup carried by the piston,an anvil beneath the-tup for supporting a workpiece during a hammeringoperation, means operable to establish a flow of'liquid under pressureinto the lower portion of the cylinder to raise the piston and thus thetup including control means operable to permit liquid'to exhaust fromthe cylinder beneath the piston whereby the piston and tup descendduring a hammering operation and the piston displaces the liquid fromthe cylinder, so that gaseous medium in the cylinder above the pistonbeing compressed during the raising of the piston and expanding as thepiston descends, compressed gaseous medium containing means operablyassociated with the cylinder above the upper limit of piston travel forreceiving a supply of gaseous medium under such pressure as to begreater than atmospheric pressure even when the piston is in itslowermost position, and controllable flow-control means for controllingcommunication between said containing means'and cylinder forcontrollably increasing the pressure of gaseous medium acting on thepiston during its. descent.

2. A drop hammer as claimed in claim 1 in which said compressed gaseousmedium containing means and said flow-control means operable to increasethe pres-- sure of gaseous medium acting on the descending pistoninclude a conduit means communicating with the cylin der above the upperlimit of piston travel, valve means associated with the conduit meansfor controlling fluid flow therethrough and a compressed air containingmeans. having said supply of medium under pressure therein incommunication with the conduit means whereby actu ation of the valvemeans admits compressed air into the cylinder above the piston.

3. A drop hammer as claimed in claim 1 in which said compressed gaseousmedium containing means and said flow control means comprise a chamberwithin the cylinder, a partition above the upper limit of piston travelseparating said chamber from the space above the piston, means by whichsaid chamber can be supplied with air under pressure, conduit meansthrough the partition, and a selectively operable valve in said conduitmeans for controllably permitting air under pressure to flow from thechamber into the space above the piston as desired.

4. A hydraulically actuated drop hammer as claimed in claim 1 in whichsaid compressed gaseous medium containing means comprises a compressedair container separate from the cylinder, a conduit means extending fromsaid container to andcommunicating with the cylinder above the upperlimit of piston travel and said flowcontrol means comprising a manuallyoperable valve in said conduit means between the container and thecylinder and operable to control communication therebetween whereby theopening of said valve admits compressed air directly into the cylinderabove the piston to augment the force of the descent thereof.

5. A hydraulically actuated drop hammer including a vertically disposedcylinder, a piston movable in the cylinder, a tup carried by the piston,means operable to establish a flow of liquid under pressure into thelower portion of the cylinder to raise the piston and thus the tupincluding control means operable to rapidly exhaust liquid from thecylinder beneath the piston whereby the tup descends during a hammeringoperation, a partition means transversely of the cylinder above theupper limit of piston travel and defining a gaseous medium containingchamber above the upper position of the piston, conduit means throughthe partition, controllable valve means in the conduit means forcontrolling communication between the chamber and the part of thecylinder accommodating the piston and conduit means incommunicationbetween the chamber and the cylinder at a location that is subjacent thepartition and also above the upper limit of piston travel whereby pluralreciprocations of the piston with said valve means closed will compressand supply the chamber with a quantity of compressed gaseous mediumunder such pressure as to be greater than atmospheric pressure when thepiston is in its lowermost position and upon such actuation of saidvalve means to open position a controllable flow of compressed mediumwill be established through the firstmentioned conduit means and intothe cylinder above the piston to controllably augment the gravitationaldescent of the piston during hammering.

6. A hydraulically actuated drop hammer including a vertically disposedcylinder, a piston movable in the cylinder, a tup carried by the piston,an anvil beneath the cylinder for carrying a workpiece to be impactedupon by the tup, means operable to establish a flow of liquid underpressure into the lower portion of the cylinder to raise the piston andthus the tup including control means operable to permit exhaust ofliquid from the cylinder so that the piston and thereby the tup falls toimpact a workpiece, said piston in falling displacing the liquid frombeneath the piston, a partition extending transversely across thecylinder above the upper limit of the piston travel, a chamber meansabove said partition, a conduit means for providing communicationbetween the chamber means and the cylinder space above the piston, aselectively operable valve means operably associated with said conduitmeans for controlling communication between the chamber means and saidspace, additional conduit means also communicating between the chamberand the cylinder at a location beneath the partition but above the upperlimit of piston travel, a nonreturn valve operably associated with saidadditional conduit means and constructed and arranged to permit air toflow from beneath the partition, through said additional conduit meansand into said chamber in response to upward movement-of the piston andwith said selectively operable valve means in a position to preventcommunication between said cylinder and chamber and said nonreturn valvemeans preventing reverse flow of air from the chamber into the cylinderbeneath the partition, said additional conduit means also having a portopening to atmosphere, said port being located between said cylinder andsaid first-mentioned non-return valve, a second non-return valveoperably associated with said port and constructed and arranged topermit air to enter said additional conduit means through said port andto flow toward the cylinder when the piston descends to prevent theescape of air from said additional conduit means whereby pluralreciprocations of said piston with said selectively operable valve meansin a position to prevent communication between said chamber means andsaid space will charge said chamber with a supply of air under suchpressure as to be greater than atmospheric pressure even when the pistonis in its lowermost position whereby subsequent actuation of saidselectively operable valve means to open position will controllablysupply compressed air into the cylinder beneath the partition tosubstantially augment the gravity fall of the piston and tup to increasethe energy of the blow struck by the tup and movable means operablyassociated with said additional conduit means and said first non-returnvalve means and constructed and arranged for selectively preventing orpermitting opening movement of said first mentioned non-return valve.

7. A hydraulically actuated drop hammer as claimed in claim 5 and asafety valve means operably associated with said chamber to permitescape of air from the chamber if the pressure in the chamber exceeds apredetermined maximum.

8. The combination with a hydraulically actuated drop hammer of the typeincluding a vertically disposed cylinder and a tup carrying pistonreciprocable in the cylinder and means for alternately admitting liquidunder pressure into the cylinder beneath the piston to raise the tup andto exhaust liquid from the cylinder so as to permit the piston and tupto fall so that the piston will displace the liquid in falling, acontainer means and associated conduit means in communication with thecylinder above the upper limit of piston travel said container meansreceiving a supply of air under such pressure as to be greater thanatmospheric pressure when the piston is in its lowermost position andselectively operable valve means operably associated with said conduitmeans for controllably establishing a direct flow of air under pressuresaid container means and into the cylinder into contact with said pistonto increase the rate of fall of the piston.

9. The combination as claimed in claim 8 in which said cylinder iselongated, a partition extending transversely across the cylinder abovethe upper limit of piston travel and defining a chamber in the cylinderabove the piston, said chamber constituting said container means, saidassociated conduit means and said valve means being incorporated in saidpartition, additional conduit means in communication between thecylinder immediately subjacent the partition and the chamber andnon-return valve means operably associated with said additional conduitmeans and constructed and arranged to permit plural reciprocations ofthe piston to establish a supply of compressed air in the chamber withsaid first mentioned valve means closed.

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